The present invention relates to a thawing device for railway track points for preventing failures in points changing due to snow or icing at the points sections of railway tracks.
Conventional types of thawing device for railway track points include, as a device for use in regions having large amounts of snow, a hot air blower type of thawing device, wherein kerosene or the like is burnt and hot air generated thereby is blown via a duct onto the points sections. Furthermore, as a device for use in regions having small amounts of snow, there is an electric heater type thawing device, wherein electric heaters are placed on the main rails and the side regions of floor plates, thereby heating the points sections.
However, these conventional thawing devices have following problems% in the case of the hot air blower type of thawing device, although the thawing capacity is excellent, there have been problems in that the heating efficiency is poor and hence fuel expenses are high, there is a risk of accidental fire, and disassembly and maintenance must be carried out in the season when the device is out of use. In the case of the electric heater type thawing device, there have been problems in that the thawing capacity is low, the rate of temperature increase is show, and ease of installation is poor, given that a special floor plate is used, and the like.
In order to increase the heating efficiency, it may be considered to use high-frequency current, but this brings a risk that the magnetic flux created by the high-frequency current may affect other devices.
Consequently, an object of the present invention is to provide a thawing device for railway track points sections which solves the above-mentioned problems by lowering running costs by means of highly efficient heating, and which secures safety by reducing the effects on other devices of the magnetic flux caused by the high-frequency current.
A thawing device for railway track points according to a first aspect of the present invention is characterized by including: a heating coil wound around a floor plate for heating the floor plate by induction; and an inverter device for supplying high-frequency current to the heating coil. By adopting this construction, the heating coil is wound around the floor plate and the heating surface area is increased, and hence the floor plate is heated at high-power with a high-frequency current, and a good effect in preventing ice formation on the floor plate and/or rails is obtained by thermal conduction from the floor plate to a main rail and tongue rails. Moreover, since the heating coil does not project significantly beyond a sleeper, it does not obstruct track maintenance work, and does not require detachment outside of the snow season.
In the aforementioned construction, it is preferred that the heating coil is wound through one or more turns in contact with the side face or the lower face of the floor plate. Thereby, the heating surface area is increased further, floor plate induction heating is performed at high-power, and a highly effective thawing capacity is achieved.
Further, it is preferred that a portion of the heating coil is wound in contact with the upper face of the floor plate. Thereby, the heating coil can be wound around the floor plate even in cases where the floor plates of the left and right-hand rails are connected, for example, at the front end portion of a railway points, or in cases where the floor plate is long.
A thawing device for railway track points according to a second aspect of the invention is characterized by including:
a heating coil wound around a floor plate for heating the floor plate by induction; an inverter device for supplying high-frequency current to the heating coil; and a protection against coil magnetism for preventing magnetic flux of the heating coil from leaking. By adopting this construction, leakage of magnetic flux from the high-frequency magnetic field generated by the heating coil is reduced, thereby reducing the effects of high-frequency noise on other devices.
In the aforementioned construction, it is preferred that the protection against coil magnetism is constituted by a cover made of a material having high resistivity and high magnetic permeability, which covers the periphery of the heating coil wound around the floor plate. Thereby, leakage of magnetic flux of the heating coil is prevented, and the effects of high-frequency noise on other devices is reduced, whilst at the same time suppressing any heating by induction of the coil magnetism prevention means itself, due to the magnetic flux.
Alternatively, the protection against coil magnetism may be constituted by first closed loop conductors disposed about the outer circumference of a single heating coil or a plurality of heating coils wound around the floor plates, and second closed loop conductors disposed around the periphery of the first closed loop conductors. Thereby, an eddy current which cancels out magnetic flux leaking from the first closed loop is induced in the second closed loop conductors, and the area peripheral to the heating coils is protected against magnetism, and the effects of high-frequency noise on other devices are reduced.
A thawing device for railway track points according to a third aspect of the invention is characterized in that a plurality of heating coils wound around floor plates for heating the floor plates by induction are connected in series by means of a feeder cable, these heating coils are connected by means of connection cables with a single inverter device for supplying high-frequency current to the heating coils, and a protection against cable magnetism is provided for preventing magnetic flux of the cables from leaking. By adopting this construction leakage of high-frequency magnetic flux generated by the cables is reduced, thereby reducing the effects of high-frequency noise on other devices.
In the aforementioned construction, it is preferred that the protection against cable magnetism is constituted by twisting the supply or return connection cables from the inverter device to the heating coils, and the feeder cable. Thereby, the magnetic fluxes induced by the high-frequency current in the supply and return cables cancel out mutually, and the area peripheral to the cables is protected against magnetism and the effects of high-frequency noise on other devices are reduced.
Alternatively, the protection against cable magnetism ay be constituted by covers which cover the periphery of the supply and return connection cables from the inverter device to the heating coils,-and the feeder cable, and which are connected in a closed loop in the vicinity of the heating coils and the inverter device. Thereby, an eddy current which cancels out magnetic flux inside the closed loop having leaked from the connection cables is induced in the covers of the closed loop, and the area peripheral to the cables is protected against magnetism and the effects of high-frequency noise on other devices are reduced.
Alternatively, the protection against cable magnetism may be constituted by superposing coils wherein portions of the supply and return connection cables are wound respectively in the same direction, to the same diameter, and through the same number of turns. Thereby, the magnetic fluxes induced by the high-frequency current in the supply and return connection cables cancel out mutually, and the area peripheral to the cables is protected against magnetism and the effects of high-frequency noise on other devices are reduced.
A thawing device for railway track points according to a fourth aspect of the Invention is characterized by including:
a heating coil for heating a floor plate by induction; an inverter device for supplying high-frequency current to the heating coil; a train detecting device for detecting the approach of a train to a points section; and an inverter controller for outputting a signal to the inverter device, the signal for either reducing or interrupting the supply of high-frequency current to the heating coil for a prescribed period of time after the approach of a train has been detected by the train detecting device. By adopting this construction, the supply of high-frequency current from the inverter device to the heating coil is either reduced or interrupted for a prescribed period of time after the approach of a train is detected. Thereby, the effects of the high-frequency noise on the high-precision equipment of the train are reduced, when the train is passing over the points section.
In the aforementioned construction, it is preferred that the train detecting device includes a magnetic field detector for converting an electrical signal into a magnetic flux and detecting changes in magnetic field caused by the approach of a train. In the magnetic flux generated by the coil or the like of the magnetic field detector, the magnetic resistance will change if a portion of a trains namely, a train wheel, is present. By detecting the changes in impedance and changes in signal current corresponding to this change, the approach of a train is detected, whereupon, for a prescribed period of time, the supply of high-frequency current to the heating coil is reduced or interrupted, thereby reducing the effects of high-frequency noise on the high-precision equipment of a train when the train is passing over a points section.
Alternatively, the train detecting device may be constituted by a signal transmitter for inputting a track path signal indicating whether a short circuit is caused between the left and right-hand rails by an axle of a train within a prescribed sections and transmitting a train present/absent signal; and a signal receiver for receiving the transmitted train present/absent signal. When a train enters the prescribed section and the left and right-hand rails are shorted by the train axle, a train present signal is output from the signal transmitter to the signal receiver, whereby the train detecting device detects that a train is passing through, or is halted in, the points section. Whereupon, the supply of high-frequency current to the heating coil is reduced or interrupted for a prescribed period of time, and hence the effects of high-frequency noise on the high-precision equipment of a train is reduced when the train is passing through a points section.